scholarly journals Dispersion and reaction in random flows: Single realization versus ensemble average

2019 ◽  
Vol 4 (12) ◽  
Author(s):  
Antoine Renaud ◽  
Jacques Vanneste
Keyword(s):  
Ensemble Average ◽  
Single Realization ◽  
Random Flows

scholarly journals Contrasting the Use of Single-Realization versus Ensemble-Average Atmospheric Dispersion Solutions for Chemical and Biological Defense Analyses

2014 ◽  
Vol 53 (6) ◽  
pp. 1399-1415 ◽  
Author(s):  
Paul E. Bieringer ◽  
Andrew J. Annunzio ◽  
Nathan Platt ◽  
George Bieberbach ◽  
John Hannan
Keyword(s):  
System Analysis ◽  
Numerical Models ◽  
Dispersion Model ◽  
Concentration Field ◽  
Ensemble Average ◽  
Time Averaging ◽  
Contaminant Concentration ◽  
Defense System ◽  
Modeling Tools ◽  
Single Realization

AbstractChemical and biological (CB) defense systems require significant testing and evaluation before they are deployed for real-time use. Because it is not feasible to evaluate these systems with open-air testing alone, researchers rely on numerical models to supplement the defense-system analysis process. These numerical models traditionally describe the statistical properties of CB-agent atmospheric transport and dispersion (AT&D). While the statistical representation of AT&D is appropriate to use in some CB defense analyses, it is not appropriate to use this class of dispersion model for all such analyses. Many of these defense-system analyses require AT&D models that are capable of simulating dispersion properties with very short time-averaging periods that more closely emulate a “single realization” of a contaminant or CB agent dispersing in a turbulent atmosphere. The latter class of AT&D models is superior to the former for performing CB-system analyses when one or more of the following factors are important in the analysis: high-frequency sampling of the contaminant, spatial and temporal correlations within the contaminant concentration field, and nonlinear operations performed on the contaminant concentration. This paper describes and contrasts these AT&D modeling tools and provides specific examples in which utilizing ensembles of single realizations of CB-agent AT&D is advantageous over using the statistical, “ensemble-average” representation of the agent AT&D. These examples demonstrate the importance of using an AT&D modeling tool that is appropriate for the analysis.

A Study on Maximum Fluctuation Width within a few Hours regarding Ensemble Average Insolation Observed at Multi-points in Large Area

2012 ◽  
Vol 132 (5) ◽  
pp. 452-458 ◽  
Author(s):  
Shinsuke Kumazawa ◽  
Takeyoshi Kato ◽  
Nobuyuki Honda ◽  
Masakazu Koaizawa ◽  
Shinichi Nishino ◽  
...  
Keyword(s):  
Ensemble Average ◽  
Large Area ◽  
Maximum Fluctuation

Entropic characterization of the coil-stretch transition of polymers in random flows

2021 ◽  
Vol 103 (3) ◽  
Author(s):  
F. Sultanov ◽  
M. Sultanova ◽  
G. Falkovich ◽  
V. Lebedev ◽  
Y. Liu ◽  
...  
Keyword(s):  
Random Flows

scholarly journals Single Chain Mean-Field Theory Study on Responsive Behavior of Semiflexible Polymer Brush

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 778
Author(s):  
Yingli Niu ◽  
Xiangyu Bu ◽  
Xinghua Zhang
Keyword(s):  
Field Theory ◽  
Message Passing Interface ◽  
Mean Field Theory ◽  
Mean Field ◽  
Algorithmic Complexity ◽  
Ensemble Average ◽  
Single Chain ◽  
Metropolis Monte Carlo ◽  
Rigid Rod ◽  
Chain Conformations

The application of single chain mean-field theory (SCMFT) on semiflexible chain brushes is reviewed. The worm-like chain (WLC) model is the best mode of semiflexible chain that can continuously recover to the rigid rod model and Gaussian chain (GC) model in rigid and flexible limits, respectively. Compared with the commonly used GC model, SCMFT is more applicable to the WLC model because the algorithmic complexity of the WLC model is much higher than that of the GC model in self-consistent field theory (SCFT). On the contrary, the algorithmic complexity of both models in SCMFT are comparable. In SCMFT, the ensemble average of quantities is obtained by sampling the conformations of a single chain or multi-chains in the external auxiliary field instead of solving the modified diffuse equation (MDE) in SCFT. The precision of this calculation is controlled by the number of bonds Nm used to discretize the chain contour length L and the number of conformations M used in the ensemble average. The latter factor can be well controlled by metropolis Monte Carlo simulation. This approach can be easily generalized to solve problems with complex boundary conditions or in high-dimensional systems, which were once nightmares when solving MDEs in SCFT. Moreover, the calculations in SCMFT mainly relate to the assemble averages of chain conformations, for which a portion of conformations can be performed parallel on different computing cores using a message-passing interface (MPI).

Rouse chain dynamics in layered random flows

1994 ◽  
Vol 49 (5) ◽  
pp. 4185-4191 ◽  
Author(s):  
G. Oshanin ◽  
A. Blumen
Keyword(s):  
Chain Dynamics ◽  
Random Flows ◽  
Rouse Chain

scholarly journals A State-of-the-Art Review on Empirical Data Collection for External Governed Pedestrians Complex Movement

2018 ◽  
Vol 2018 ◽  
pp. 1-42 ◽  
Author(s):  
Xiaomeng Shi ◽  
Zhirui Ye ◽  
Nirajan Shiwakoti ◽  
Offer Grembek
Keyword(s):  
Data Collection ◽  
Empirical Data ◽  
Empirical Studies ◽  
Movement Patterns ◽  
Simulation Models ◽  
Straight Line ◽  
Challenges And Opportunities ◽  
Pedestrian Traffic ◽  
Random Flows ◽  
Complex Movement

Complex movement patterns of pedestrian traffic, ranging from unidirectional to multidirectional flows, are frequently observed in major public infrastructure such as transport hubs. These multidirectional movements can result in increased number of conflicts, thereby influencing the mobility and safety of pedestrian facilities. Therefore, empirical data collection on pedestrians’ complex movement has been on the rise in the past two decades. Although there are several reviews of mathematical simulation models for pedestrian traffic in the existing literature, a detailed review examining the challenges and opportunities on empirical studies on the pedestrians complex movements is limited in the literature. The overall aim of this study is to present a systematic review on the empirical data collection for uni- and multidirectional crowd complex movements. We first categorized the complex movements of pedestrian crowd into two general categories, namely, external governed movements and internal driven movements based on the interactions with the infrastructure and among pedestrians, respectively. Further, considering the hierarchy of movement complexity, we decomposed the externally governed movements of pedestrian traffic into several unique movement patterns including straight line, turning, egress and ingress, opposing, weaving, merging, diverging, and random flows. Analysis of the literature showed that empirical data were highly rich in straight line and egress flow while medium rich in turning, merging, weaving, and opposing flows, but poor in ingress, diverging, and random flows. We put emphasis on the need for the future global collaborative efforts on data sharing for the complex crowd movements.

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